Element substrate and printed wiring board

ABSTRACT

An element substrate includes a plurality of terminals, a first receiving circuit and a second receiving circuit each receiving a differential signal via one of the terminals included in the plurality of terminals, a driving circuit including a first input unit for inputting a first signal and a second input unit for inputting a second signal and driving a driving element based on the first signal and the second signal, and a setting circuit for setting a first connection state of connecting an output from the first receiving circuit to the first input unit and connecting an output from the second receiving circuit to the second input unit, and a second connection state of connecting an output from the first receiving circuit to the second input unit and connecting an output from the second receiving circuit to the first input unit based on an externally input signal.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a printed wiring board having anelement substrate and a differential signal line for inputting adifferential signal.

2. Description of the Related Art

Japanese Patent Application Laid-Open No. 2007-296638 discusses afull-line recording head. A plurality of recording element substrates isarranged in a staggered pattern on a printed wiring board of therecording head.

A clock signal (CLK) is a commonly-used signal in the recording elementsubstrates, and one-to-many connection (multi-drop connection) isdesired from the viewpoint of wiring space of the printed wiring board.On the other hand, since different signals are used for the recordingelement substrates as image data signals (DATA), one-to-one connection(Point-to-Point connection) is desired.

Developments for attaining higher frequency and speed of the image datasignal and the clock signal are in progress to attain a high speedrecording operation and high image quality. Therefore, it is necessaryto keep a stub (branch wiring) as short as possible to ensure goodwaveform quality when performing the one-to-many connection (multi-dropconnection) in wiring of signal lines.

However, in the state where the recording element substrates arearranged in a staggered pattern, a length of the stub is increased.Therefore, since effective characteristic impedance of the signal lineis reduced, signal reflection tends to occur, and an amplitude of eachof the signals is reduced, resulting in deterioration of signal waveformquality.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, there is provided anelement substrate including a plurality of terminals, a first receivingcircuit and a second receiving circuit each receiving a differentialsignal via a predetermined terminal included in the plurality ofterminals, a driving circuit including a first input unit for inputtinga first signal and a second input unit for inputting a second signal anddriving a driving element based on the first signal and the secondsignal, and a setting circuit for setting a first connection state ofconnecting an output from the first receiving circuit to the first inputunit and connecting an output from the second receiving circuit to thesecond input unit and a second connection state of connecting an outputfrom the first receiving circuit to the second input unit and connectingan output from the second receiving circuit to the first input unitbased on an externally input signal.

Further features and aspects of the present invention will becomeapparent from the following detailed description of exemplaryembodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate exemplary embodiments, features,and aspects of the invention and, together with the description, serveto explain the principles of the invention.

FIGS. 1A and 1B are diagrams each illustrating a circuit layout of arecording element substrate 101.

FIG. 2 is a plan view illustrating a printed wiring board 103.

FIG. 3 is a partially enlarged view illustrating a part of FIG. 2.

FIG. 4 is a plan view illustrating a printed wiring board to which thepresent invention is not applied.

FIGS. 5A and 5B are diagrams each illustrating a simulation result of anamplitude of a signal.

FIG. 6 is an exploded perspective view illustrating a recording head.

FIGS. 7A and 7B are diagrams each illustrating a recording elementsubstrate.

FIG. 8 is a diagram illustrating a relationship between a recording headand a conveyance direction of a recording medium 800.

DESCRIPTION OF THE EMBODIMENTS

Various exemplary embodiments, features, and aspects of the inventionwill be described in detail below with reference to the drawings.

FIG. 1A is a diagram illustrating a circuit layout of a recordingelement substrate 101 as an element substrate. The recording elementsubstrate 101 includes a receiving circuit 303, a switching circuit 305,a driving circuit 304, a switching control circuit 306, a controlterminal 308, and terminals (pad) 204.

The receiving circuit 303 includes two circuits (303-1, 303-2) forreceiving differential signals. The driving circuit 304 includes a firstinput unit for inputting a clock signal CLK (first signal) and a secondinput unit for inputting a data signal DATA (second signal). The drivingcircuit 304 drives a recording element based on the first signal and thesecond signal. The terminals 204 are arranged along a direction of anarrow B.

An output from the first receiving circuit 303-1 and an output from thesecond receiving circuit 303-2 are input into the switching circuit 305.In the switching circuit 305, it is possible to set a first connectionstate of connecting the output from the first receiving circuit to thefirst input unit and connecting the output from the second receivingcircuit to the second input unit, or a second connection state ofconnecting the output from the first receiving circuit to the secondinput unit and connecting the output from the second receiving circuitto the first input unit.

The switching circuit 305 switches between the first connection stateand the second connection state based on a signal input from the controlterminal 308. For example, the first connection state is set when alogical level of the signal input from the control terminal 308 is a lowlevel, while the second connection state is set when the logical levelof the signal input from the control terminal 308 is a high level. Inother words, the switching circuit 305 is a setting circuit for settingthe signal connection.

Illustrated in FIG. 2 is a configuration of the printed wiring board 103in which the recoding element substrates 101 are provided. Six recordingelement substrates 101 are provided on the printed wiring board 103. Aregion 401 (first region) and a region 402 (second region) are definedfor the recording element substrates 101, so that the plurality ofrecording element substrates 101 is arranged along a predetermineddirection (arrow A) as illustrated in FIG. 2.

A signal line pair (first differential signal lines) for supplying theclock signals is arranged in a region 403 (third region) defined betweenthe region 401 and the region 402. Signal lines 301 are branched in theregion 403. A signal line pair (second differential signal lines) 302for supplying the data signals is arranged in a region 404 (fourthregion) defined outside the region 401 and the region 402.

The printed wiring board 103 is provided with terminal arrays 107 eachhaving a plurality of terminals for signal connection with the recordingelement substrate 101. Also, the printed wiring board 103 is providedwith a terminal array 108 having a plurality of terminals for signalconnection with another substrate.

FIG. 3 is a partially enlarged view illustrating a part of FIG. 2. Theterminals included in the terminal arrays 107 of the printed wiringboard are connected to the terminals 204 of the recording elementsubstrate 101 by wire bonding 309. Termination of the signal lines isperformed using a resistor 310 (the signal lines are short-circuited viathe resistor 310) in the recording element substrate 101.

Referring to FIG. 3, the termination of the signal line pair (seconddifferential signal lines) of one-to-one connection is performed by theresistor 310 in each of the recording element substrates 101. The signalline pair (first differential signal lines) of one-to-many connection isconnected only to the termination resistor 310 for the termination inthe recording element substrate 101-6.

Referring to FIG. 3, a high level signal (e.g. source voltage VDD) issupplied to each of the control terminals 308 of the element substrates101-2, 101-4, and 101-6. A low level signal (e.g. earth VSS) is suppliedto each of the control terminals 308 of the element substrates 101-1,101-3, and 101-5.

When a control signal is input to the element substrate 101 from thecontrol terminal 308, the switching circuit 305 is in the connectionstate illustrated in FIG. 3. As described above, the connection state ofthe switching circuit 305 is set by inputting the control signal inputfrom the external part of the element substrate 101.

With the above-described configuration, it is possible to connect thereceiving circuit that is closer to the differential signal lines 301(clock signal) in the configuration that each of the recording elementsubstrates 101 includes the plurality of receiving circuits. Forexample, the receiving circuit 303-2 of the recording element substrate101-2 is connected to the differential signal lines 301 (clock signal).

Also, the receiving circuit 303-1 of the recording element substrate101-3 is connected to the differential signal lines 301 (clock signal).Thus, it is possible to suppress a length of the stub 307 of thedifferential signal lines 301, thereby suppressing signal reflection anddeterioration of signal quality.

FIG. 1B is a diagram illustrating a second exemplary embodiment. Sincethe switching circuit 305, the driving circuit 304, and the like of theelement substrate 101 are the same as those of the first exemplaryembodiment, description thereof will not be repeated. FIG. 1B isdifferent from FIG. 1A by the positions of the terminals 204, and theterminals 204 are arranged along an arrow A in FIG. 1B. Thus, it ispossible to suppress the length of the stub 307 of the differentialsignal lines 301 provided in the region 403 illustrated in FIG. 2,thereby suppressing signal reflection and deterioration of signalquality.

The exemplary embodiments of the present invention have been describedabove. Illustrated in FIG. 4 is a plan view of a printed wiring boardwhen the present invention is not applied. As illustrated in FIG. 4, thepositions of the receiving circuits of the recording element substrates101-2 and 101-4 are distant from the differential signal lines 301.Therefore, a length of the stub 307 connecting to the recording elementsubstrates 101-2 and 101-4 are longer than the stub 307 connecting tothe recording element substrates 101-1, 101-3, and 101-5.

FIGS. 5A and 5B are diagrams each illustrating a simulation result of anamplitude of a transferred signal. Illustrated in FIG. 5A is the signalamplitude when the present invention is applied (state of FIG. 2).Illustrated in FIG. 5B is the signal amplitude when the presentinvention is not implemented (state of FIG. 4).

The minimum amplitude is 177 mV when the present invention isimplemented (FIG. 5A), while the minimum amplitude is 77 mV when thepresent invention is not applied (FIG. 5B). It is apparent that thedifference between the signal amplitudes is about 100 mV. In otherwords, signal quality is largely improved by implementing the presentinvention, thereby realizing suppression of data transfer errors.

(Description of Recording Head)

A recoding head will be described as one example of a device. FIG. 6 isan exploded perspective view illustrating a recording head. A recordinghead 100 includes recording element substrates 101, a support member102, a printed wiring board 103, an ink supply member 104, and the like.In FIG. 6, six recording element substrates 101 are arranged in astaggered pattern. It is possible to obtain a recording head having alarger print width by increasing the number of recording elementsubstrates 101 to be mounted.

The recording element substrate 101 is a device for discharging an ink,including a Si substrate 701 having a thickness of 0.05 to 0.625 mm andprovided with a long groove-like ink supply port 702 formed by wetetching, dry etching, or the like with high accuracy as illustrated inFIG. 7.

A plurality of heaters 703 and driving circuits (recording element),which are arranged across the ink supply port 702, and each of which isprovided for driving one of the heaters 703 at a predetermined positionfor a predetermined time are formed on a surface of the Si substrate 701by a film formation technique, and a terminal 204 for electricalconnection to the printed wiring board 103 is formed at each of oppositeends in a longitudinal direction of the recording element substrate 101.

Also, a discharge port forming member 705 made from a resin material isformed on the Si substrate 701, and a plurality of discharge ports 706corresponding to the heaters 703 and an ink storage chamber 707 areformed by a photolithography technique.

In FIG. 6, the support member 102 is a member for supporting and fixingthe recording element substrate 101 and formed from alumina (Al203)having a thickness of 0.5 to 10 mm, for example. The material of thesupport member 102 is not limited to alumina, and a material having alinear expansion rate similar to the recording element substrate 101 andhigh rigidity, may be used. Examples of the material include silicon(Si), aluminum nitride (AlN), zirconia, silicon nitride (Si₃N₄), siliconcarbide (SiC), molybdenum (Mo), tungsten (W), and the like.

An ink supply port 105 is formed on the support member 102 at a positioncorresponding to the ink supply port 702 of the recording elementsubstrate 101. The recording element substrate 101 is fixed to thesupport member 102 by bonding with a first bonding agent with highposition accuracy.

The printed wiring board 103 is a member for transmitting and supplyingan electric signal and a source voltage to the recording elementsubstrate 101 for discharging the ink, and, for example, a flexiblewiring board having a two-layer structure in which a wiring is formed oneach of both sides of the substrate and a surface layer is covered witha protection film, is used.

As illustrated in FIG. 6, the printed wiring board 103 has openings 106for mounting the recording element substrates 101. The printed wiringboard 103 has terminals 107 corresponding to the input terminals 204 ofthe recording element substrates 101 and a terminal (e.g. connector) forreceiving the electric signal from a recording device main body.

The printed wiring board 103 is fixed by bonding with a second bondingagent to the surface of the support member 102 on which the recordingelement substrates 101 are bonded. Gaps between the openings 106 and therecording element substrates 101 are sealed with a sealant.

The terminals 107 of the printed wiring board 103 and the inputterminals 204 of the recording element substrates 101 are electricallyconnected to each other by a wire bonding technique or the like using agold wire, and eclectic connection parts are sealed with a sealant. Theprinted wiring board 103 is bent and fixed at each of both sides of thesupport member 102, so that electric connection with the main body iseasily performed.

The ink supply member 104 is a member for supplying the ink from an inktank to the recording element substrates 101 and, for example, formed byinjection molding using a resin material. An ink storage chamber 109 forsupplying the ink to the plurality of recording element substrates 101is formed in the ink supply member 104. The ink is introduced from theink tank to the ink storage chamber 109 via an ink supply tube throughan opening 110. The ink supply member 104 is bonded to the supportmember 102.

(Description of Recording Element Substrate)

As one example of the element substrate 101, a recording elementsubstrate serving as a driving element for driving a recording elementwill be described. FIGS. 7A and 7B are diagrams illustrating therecording element substrate 101. As illustrated in FIG. 7A, terminals704 for electrical connection to the printed wiring board 103 are formedat each of opposite ends in a longitudinal direction of the recordingelement substrate 101. Two discharge port arrays including a pluralityof discharge ports are formed.

FIG. 7B is a sectional view illustrating the recording elementsubstrate. A long groove-like ink supply port 702 is formed on a Sisubstrate 701 having a thickness of 0.05 to 0.625 mm by wet etching, dryetching, or the like with high accuracy. A plurality of heaters(recording elements) 703 and driving circuits for driving the heaters703 are formed by a film formation technique on the surface of the Sisubstrate 701.

A discharge port forming member 705 made from a resin material is formedon the Si substrate 701, and a plurality of discharge ports 706corresponding to the heaters 703 and an ink storage chamber 707communicated with the discharge ports 706 are formed by aphotolithography technique.

(Description of Recording Device)

FIG. 8 is a diagram illustrating a relationship between a recording headand a conveyance direction of a recording medium 800, which is viewedfrom a back side of the recording medium 800. In a recording operation,the recording head is fixed in the recording device, and the recordingmedium 800 is conveyed, followed by discharge of the ink from theplurality of discharge ports 206 on the recording element substrates101, thereby forming an image on the recording medium 800. The recordingdevice includes a conveying unit for conveying the recording medium 800.

Though the first and second exemplary embodiments are described above,the present invention is not limited to the above-described exemplaryembodiments. For example, though the number of the element substrates tobe provided on the printed wring board 103 is six in the above exemplaryembodiments, the number is not limited thereto and may be four, eight,ten, or the like. Also, the driving element may be a light emittingelement such as a light emitting diode (LED), and a sensor element suchas a complementary metal oxide semiconductor (CMOS) sensor. As examplesof the device, the present invention may be applied to a reading unitfor reading an image of an original document, a display unit fordisplaying an image, and the like. The signals to be received by thereceiving circuit are not limited to the clock signal and the datasignal, and other control signals may be received.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all modifications, equivalent structures, and functions.

This application claims priority from Japanese Patent Application No.2010-112291 filed May 14, 2010, which is hereby incorporated byreference herein in its entirety.

1. An element substrate comprising: a plurality of terminals; a firstreceiving circuit and a second receiving circuit each configured toreceive a differential signal via a predetermined terminal included inthe plurality of terminals; a driving circuit including a first inputunit for inputting a first signal and a second input unit for inputtinga second signal and configured to drive a driving element based on thefirst signal and the second signal; and a setting circuit configured toseta first connection state of connecting an output from the firstreceiving circuit to the first input unit and connecting an output fromthe second receiving circuit to the second input unit, and a secondconnection state of connecting an output from the first receivingcircuit to the second input unit and connecting an output from thesecond receiving circuit to the first input unit based on an externallyinput signal.
 2. The element substrate according to claim 1, wherein thefirst signal is a clock signal, and the second signal is a data signal.3. The element substrate according to claim 1, wherein the drivingelement is a recording element.
 4. A printed wiring board comprising: afirst region and a second region each of which is defined for arrangingtherein a plurality of the element substrates according to claim 1 alonga predetermined direction; first differential signal lines arranged in athird region defined between the first region and the second regionalong the predetermined direction; second differential signal linesarranged in a fourth region defined outside the first region and thesecond region; and terminals connected to the first and seconddifferential signal lines.